Featured image on Mystique theme is smaller than usual

Hello,
I have been using Mystique for close to 1 year and the featured image has always worked very well. the featured picture was displayed across the screen. Lately, however, my featured pictures are small and almost boxed into a square. Please help me figure out what the issue is. The blog I need help with is http://nanastastytraditions.wordpress.com

I was able to edit the image and crop it to a shape closer to the header, which filled the screen width more, but I don't know why the automatic cropping has disappeared. I would also like to see the automatic feature fixed.